China's star swimmer Sun Yang is ready to defend gold in Rio

— -- NORWALK, Conn. -- This serene Southern Connecticut coastal city received a group of special guests in July. They came from half a world away, making a short visit before heading to Rio de Janeiro in August.

For three weeks, the Swim Seventy Aquatic Center, a swanky private facility, was home to the Chinese Olympic swim team. Far away from the intense media attention in Beijing, the Olympians trained twice a day, putting the finishing touches to their preparations for the world's biggest international sporting event.

"He looks pretty good," a member of the coaching staff told Zhang Yadong, Sun's personal instructor.

"He's been in a good mood lately." Zhang said with a smile.

"Looking back at the preparations in the past month or two, everything is pretty good," Sun told ESPN.com in an exclusive interview.

But for Sun, as well as people around him, this kind of optimism has been hard to come by since the 24-year-old suffered a foot injury during a January training session in Australia.

Sun's mother, Yang Ming, said her heart "thumped" after learning of her son's injury. Sun also told Chinese state media news agency Xinhua that the injury was so painful he almost cried.

In the following months, Sun's injury shadowed him, as well as entire Chinese team. The road to recovery was long and tedious. He began to walk on crutches in February. By March, he was able to swim, relying on strength from only one leg. Little by little, Sun was overcoming fear while racing against the clock.

"Some lost some progress in training because of the injury," Sun said. "I was doing my best to overcome the obstacles and come back tenaciously."

Prior to coming to Connecticut, Sun was training by himself in California, surviving a dull and arduous period filled with countless drills and treatments, as well as a two-hour daily commute to and from the facility.

Sun tried to keep everything to himself. Speaking to ESPN.com, Sun's mother pulled up a photo on her cell phone, showing Sun's body and arms covered with medical patches after a treatment.

"He won't let me take pictures or share them on WeChat [a Chinese mobile social media platform]," Yang said. "I took this one secretly."

With the help from his family and the swim team, Sun's recovery was speedy. Last June, he won the 200-meter freestyle competition at the 2016 Arena Pro Swim Series in Santa Clara with a 1:44.82 result, the best record in the world so far this year.

In Rio, Sun will compete in 200-, 400- and 1,500-meter freestyle events. To defend the 400 and 1,500 gold medals he won four years ago in London, Sun will have to face several challengers. One is Italy's Gregorio Paltrinieri, who won the 1,500 freestyle gold at last year's World Swimming Championships after Sun withdrew from the final due to injury.

In the 400 freestyle, Sun will face South Korea's Park Tae-hwan, a tough foe in the pool but a friend outside of it, who lost the gold to Sun in London. In the 200 freestyle, Sun will meet Japan's rising star Kosuke Hagino, Great Britain's World Swimming Championships gold medalist James Guy, and 27-year-old American Conor Dwyer.

"I am happy with my confidence level." Sun said. "I haven't swam a lot this year, but I feel like I am in pretty good shape after competing in two events. Everything, including my final sprints, has increased a lot compared to two years ago. The recovery has also been pretty good."

As China's best swimmer, Sun carries the heaviest weight, trying to help his country get ahead on the medal counts list. To ensure Sun's training quality in Norwalk, the Chinese team provided him with the best practice time slots, a team doctor and a therapist, as well as his own car.

"As a defending Olympic champion to compete this year," he said, "I think I will have an edge over my rivals in terms of confidence and experience."

Outside the pool, the 6-foot-6 Sun is a big basketball fan. He shoots hoops with his father during free time. While in California, Sun watched this year's NBA Finals Game 5 in Oakland, witnessing LeBron James and the Cleveland Cavaliers start their comeback back from a 3-1 deficit.

"I love watching Steph Curry and the Golden State Warriors, but at that moment I wanted LeBron to win, because he is the best," he said.

The Chinese swimming team has since left Connecticut for Rio, and will settle into the Olympic Village in early August. Three weeks of training in the U.S. has allowed Sun to get into his best form. But now he just has to prove he is the best.

On Monday, Sun Yang wrote on his Weibo (a Chinese social media platform): "Third time heading to the Olympics, it is my utmost responsibility to win honor for my country. I'll strive to make my dream come true. No matter how harsh and exhausting the training is, I have no complaints or regrets. Rio, here we come."